Stethoscopic spectrograph



June 8, 1965 J. w. TRUMPY ETAL 3,188,645

S TETHOSGOP I C SPECTROGRAPH Filed Sept. 26, 1963 8 Sheets-Sheet 1 `7f3/eeuw igg f 0%# www# June 8, 1965 J. w. TRUMPY ETAL STETHOSCOPIC SPECTROGRAPH 8 Sheets-Sheet 2 Filed Sept. 26, 1963 June 8, 1965 J. w. TRUMPY ETAL 3,188,645

STETHSCOPIC SPECTROGRAPH Filed sept. 26, 1963 l 8 Sheets-Sheet 3 28% Woof/Aral QZ *A6/SQ. /22 (fm/fe/N il Q 5 June 8, 1965 .1. w. TRUMPY ETAL 3,188,645

STETHOSCOPIC SPEGTROGRAPH Filed sept. ze, 196s s sheets-sheet 4 ALL June 8, 1965 J. w. TRUMPY ETAL 3,188,645

S'IETHOSCOPIC SPECTROGRAPH June 8, 1965 J. w. TRUMPY ETAL STETHOSCOPIC SPECTROGRAPH 8 Sheets-Sheet 6 Filed Sept. 26, 1963 8 Sheets-Sheet 7 June 8, 1965 J. w. TRUMPY ETAL STETHOSCOPIC SPECTROGRAPH Filed Sept. 26. 1965 June 8, 1965 J. w. TRUMPY ETAL 3,188,645

STETHOSCOPIC SPECTROGRAPH Filed Sept. 26, 1963 8 Sheets-Sheet 8 iig. 1b.

United States Patent O 3,158,645 S'EETHOSCPC SEECTRGRAPH Jay W. Trumpy, Pacific Palisades, and Hubert iitiand and Melvin 0. vitt, Los Angeles, Calif., assignors to Douglas Aircraft Company, Inc., Santa Monica, Calif.

Filed Sept. 26, 1963. Ser. No. 311,691 19 Claims. (Cl. 34am-33) Our invention relates generally to means for analyzing and recording signals of a periodic nature. More particularly, the invention relates to an instrument useful in medical diagnosis of, for example, heart trouble, which will record and identify the sounds made by the action of individual parts of the heart.

The stethoscope is a well-known instrument which can be used in the diagnosis of heart trouble. The heart sounds heard through the stethoscope must, of course, be properly analyzed or interpreted by a competent heart specialist in order to obtain any idea as to the possible or probable trouble .in the heart. Such conclusions are based largely on the experience of the physician in relating certain sounds to known sounds which are characteristic of different types of heart trouble. For example, a defective mitral valve would normally produce certain characteristic sounds that might be recognized by a heart specialist. Admittedly, it is extremely difiicult to obtain an accurate analysis and diagnosis with any reasonable certainty of the specific nature of any heart trouble solely by means of a stethoscope. One of the difficulties here resides in the fact that a written record of the sounds is not available for careful study from an instrument such as the ordinary stethoscope.

The well-known electrocardiograph does provide a written record or graph which is a timewise plot of the electrical potential of the impulse signal that triggers the heart for each heart beat. It does not, however, operate on the basis of heart sounds and does not provide as much useful information to a heart specialist as does the stethoscope. The electrocardiograph is, of course, extremely useful for diagnosis of certain aspects of hea-rt trouble, but to the experienced heart specialist, the stethoscope is an indispensible instrument for obtaining fundamental and critically important information of the heart.

Bearing in mind the foregoing, it is a major object of our invention to provide a stethoscopic device which will produce a written record or graph based upon heart sounds and is particulraly useful for diagnosis of heart disorders.

Another object of the invention is to provide an instru ment which will produce recordings of heart sounds wherein an accurate and comprehensive analysis can be made from such recordings to specifically determine various heart defects.

A further object of the invention i-s to provide a stethoscopic spectrograph which Will produce recordings of heart sounds that are clearly illustrative of the specific nature and location of any defects of the heart.

A still further object of this invention is to provide a heart sound spectrograph which will produce recordings of a uniform size over a wide range of different repetition rates of heart beats. v

Briefly, and in general terms, the foregoing and other objects are preferably accomplished by providing an instrument which includes a carriage that can be moved in a lateral direction above the surface of suitable recording paper, the kcarriage in turn mounting pen means which is longitudinally movable with respect to the surface of the paper, microphone means adapted to pick up periodic sounds such as those of heart beats and convert these sounds into an electrical signal, means for amplifying the electrical signal, means adjustably coupled with the carriage and responsive to lateral movement thereof for 3,188,645 Eatented .lune 8, 1965 r. ICC

selectively obtaining successive frequency components of the amplified electrical :signal and recording the frequency components on the paper by the pen means in its longitudinal movement in contact with the surface of the paper,

filter means for obtaining a predominant, recurrent, synchronizing signal from the amplified electrical signal, and

means for varying the speed of the pens according to the repetition rate of the predominant, synchronizing signal whereby recordings of uniform size having markings thereon indexed to similar reference points, are produced ver a wide range of different rates of heart beats.

Structurally simplied versions of our invention have been provided by modifying certain parts thereof. ln one version, a manually set stepper motor drive is utilized for driving the pens, and in another version, the carriage has been eliminated and only a single motor is used to drive both pens and paper.

Our invention will be more fully understood, and other objects and features will become apparent from the following detailed desc-ription of illustrative examples of the invention to be taken in connection with the attached drawings, in which:

EEGURE l is a perspective View of an illustrative embodiment of our invention;

FGURE 2 is a prospective View of the carriage portion of the invention shown in FIGURE 1;

FEGURE 3 is a schematic block diagram of the invention shown in FIGURE 1;

FIGURE 4 is a wiring diagram of an illustrative modulator circuit for the invention;

FEGURE 5 is a wiring diagram of an illustrative heterodyne oscillator circuit for the invention;

FGURE 6 is a wiring diagram of an illusrtative intermediate frequency amplifier for this invention;

FIGURE 7 is a wiring diagram of an illustrative penwrite control circuit for this invention;

FiGURE 8 is a wiring diagram of an illustrative syn chronizing signal filter for the invention;

FGURE 9 is a wiring diagram of an illustrative artificial heart beat `generator circuit and power pulse circuit for the invention;

FIGURE l() is a drawing showing a recording including various illustrative formations produced by the invention on a section of paper;

FIGURE ll is a graph relating operation of the invention with various pen speeds FIGURE 12 is a schematic block diagram of a modified form of the invention;

FIGURE 13 is a perspective View, somewhat fragmentary, of another version of our invention; and

FEGURE 14 is a circuit diagram for the version of invention shown in FIGURE 13.

FIGURE 1 is a perspective view of an illustrative embodiment of our stethoscopic spectrograph. The spectrograph 2@ includes a generally rectangular carrying case 22 having a normally lower body portion 24 and an upper hinged lid 26. The lid 26 may be held up by the pinjointed brace arm 26a and 26h. The front panel 24a of the body portion 24 has an oval cutout Zeb which is preferably covered with a suitable imesh grid 24C. A speaker (not visible) is mounted to the front panel 24a directly behind the cutout Zlib.

A control panel 23 is located near the front of the top panel 24d of the body portion 24. The control panel 2S includes jacks 23a and 28h into which are plugged the lead ends of a stethoscopic microphone 3i) and a headphone 32, respectively. The microphone 3f) and headphone 32 may be stored in drawer 34 which is adapted to slide into and out of the side panel 24e. The drawer 34 can also be used to store graph paper. The paper 36 is suitably positioned on top of a somewhat raised, flat platen 3S and is electrically marked by pens 40 such as the three pens 40a, 40b .and 40C.

The platen 38 may be hollow, having a large number of small apertures in its upper surface connecting with the hollow interior of the platen 38. The hollow interior of the platen 38 is connected to `a suitable vacuum source to produce a relatively light vacuum through the platen apertures which causes the paper 36 to be held flat against the platens surface. The markings on the surface of the paper 36 are not disrupted by the platen apertures because of their smallsize. A suitable vacuum can be produced by driving a small'suction pump or motor (not shown) through an appropriate drive connection to the motor 63 (see FIGURE 2).

The three pens 40a, 4% and 40e are equidistantly mounted circumferentially on a closed band 42, and the band 42 is, in turn, mounted on pulleys 44a and 44h which are respectively affixed to the ends of two vertical and rotatable shafts 46a and 4Gb. The shafts 46a and deb are rotatably mounted to the arms 48a and 48b, respectively, of plate structure 48C of the carriage 4S. The carriage 48 is progressively moved from a front position rearwardly to a back position as the pens 40 are moved around their loop. Pulleys 44a and 44b are structurally designed with peripheral weight orientation to provide a certain amount of ywheel eifect. Y

`FIGURE 2 is a perspective view of the carriage 48 and its drive system. The carriage t8 preferably has aflixed centrally to the normally lower surface thereof, a split nut i) which engages a lead screw 52. The nut 56D may be expanded or widened by a suitable release mechanism 54 to disengage the halves of the split nut 5@ from the threads of the lead screw 52. The split nut 5t) can be used to disengage the carriage 48 from the lead screw 52 so that the carriage 48 can be manually pulled back, if desired, to reset or adjust it as may be required.

The mechanism 54 can comprise a lever-spring arrangement for widening the halves of the split nut 5u by means of a lever mechanism acting against the force of a spring which normally causes the halves of the nut 5t? to engage the threads of the lead screw 521. The mechanism 5ft may, alternatively, comprise a screw arrangement wherein the halves of the nut 5@ are moved together or apart by rotation of a screw connecting and holding the halves of the nut 5) in any xed and precise separation. Other suitable mechanisms may, of course, be used.

The lead screw 52 is rotatably supported at its ends in bearings (not shown) which are suitably mounted to fixed structure of the lower body portion 2d of the carrying case 22. The plate structure 48e is also supported by suitable rollers (not shown) engaging xed structure of the body portion 24, to permit reciprocating movement of the carriage 48. The various cooperative bearings, rollers and supporting structure along with other similar matter have been omitted from FlGURE 2 for clarity of illustra'- tion, of course, and are not necessary to show for an understanding of our invention.

A pulley 56 is affixed near one end of the lead screw 52 and is rotated in one direction or the other by a belt 58 which is driven by the upper half of another pulley 60 that is mounted near the upper end of a vertical shaft 62. The pulley 60 is axially axed to the vertical shaft 62 which also mounts a large friction wheel 64 that is engaged by a smaller friction wheel66. The wheels ed and 66 can, of course, be .a meshing gear and pinion. The

Vsmaller wheel 66 is mounted on the output shaft of a motor 68. The lower half of the pulley dii drives a'belt 7 il which engages the drive pulley 72a of aone-way clutch 72. A sprocket wheel '74 is mounted on the output shaft 72b of the one-way clutch 72 and engages pcrforations or holes 36a in the paper 36 to drive the same.

When the motor 68 is energized to rotate in one `direction, the carriage 4S is moved by lead screw 52 from a forward position to the rear ofthe carrying case ZZ, and whenthe motor 68 is energized to rotate in the opposite direction, the carriage 43 is moved from a rearward position forward towards the front of the case 22 to reset the carriage 4S for another recording. The one-way clutch 'i2 is engaged to drive the paper 3d when the carriage i8 is being driven forwardly to return towards the front of the carrying case 22.

Another motor 76, smaller than the motor 68, is mounted to the lower surface of the arm itin to drive the shaft den and its pulley 44a. The band 4Z is under tension between pulleys Ma and Mb, and is frictionally driven by thepulley 44a. Of course, the pulleys da: and 3i-tb can be gears instead, and the band 42 can be suitably toothed to mesh with the teeth on such gears. Thus, the pens dii are driven repeatedly around, and as each pen moves from pulley ida to pulley 44H9, the pen engages the paper 36 on the raised platen 38 (FIGURE l) and sweeps across it in a straight line. The pens riti produce visible marks when they are electrically energized by a control circuit described later. f

While three pens Alda, 4Gb and Llite are shown, a greater or lesser number of equally spaced pens may be used. However, the speed of the motor 76 should be such in comparison with the speed of motor 63 and its driving mechanism, that the cyclic speed of the pens d@ in Sweeping longitudinally across the paper 36 is relatively fast with respect to the lateral (front to rear direction) speed of the carriage dd. Thus, as the carriage 43 moves from a forward position in which a pen it? would sweep across the paper 3d near the forward edge thereof, a relatively large number of parallel longitudinal sweeps would be made by the pens across the paper 36 as the carriage moves to its back or rear position.

The parallel longitudinal sweeps are preferably closely spaced laterally ladjacent to each other but not contiguously so, however. It is readily apparent, of course, that each pen itl engages the paper 136 only as it moves from the front of pulley 44a 4to the front of pulley Mb because of the raised condition of the paper 3o on the platen 3d, which permits the points of the pens 4@ to touch or bear on the surface of the paper 36. The pens di? do not write when traveling bet-Ween the rear of pulleys 44a and 44!) because the ends or tips of the pens 4G circumscri'be a lateral diameter about each pulley which is greater than the width of the paper 316.

A control switch 7S having a frictiona-lly held arm '7&1 is operated with movement of the carriage 4d. The arm 78a remains set in Vany position by friction. However, the arm 78a is normally in one position engaging a contact 78h or in another position engaging another contact 78C. The farm 78a itself is connected to a voltage source supplying 28 volts, `for example, the Contact 78h is `connectcd Vto the control coil 80a of a relay 8u, and the contact 7de is not connected to anything. The 'arm '78a is, of course, suitably insulated from Ithe plate .structure 48e and stop pins 82a and b2b which are affixed to structure of the carrying case 22.

The pins 82a and 8211 are positioned with respect to the carriage 48 so that the arm '78a 'engages the pins near the respective limits of rearward and forward travel for the carriage 48. For example, as the carriage i3 nears its rearward limit of travel, the arm 73a engages the pin 82a as shown in FIGURE-2 and rotates the arm 78a until it engages the contact 7 8b. The control coi-l Stia is energized to actuate the relay Sil which causes reversal of the motor 68. The pens 46 are stopped from their cyclic movement and the ycarriage 4S is moved from its rearward limit posi- -tlon forwardly. At the same time, the one-way clutch 72 is engaged to advance thepaper 36 a proper amount.

The arm 73a is frictionally held in engagement with the Contact '78h until the carriage 48 nears its forward limit position. The arm 78a then engages the pin 82h which opens the circuit connecting power to the contro-l coil dan to rie-energize the relay Sii. When the relay 80 is deenergized, the motor 68 is reversed to start driving the carriage 4S in a rearward direction. The machine is now reset -for recording another pattern on a section of the paper 36, and its power can be turned off at this time if another recording pattern is not desired. When it is desired to make the next recording pattern, power to tl e machine is (manually) turned on. The motors d8 and '76 are `again energized -to drive the carriage 4h and the pens 40. It is noted that the carriage t8 momentum is enough, and the distance between contacts 7b `and 7de is such that the arm 73a is brought to engage the contact 78e for reset. The arm 78a is then frictionally hel-d in engagement with contact '78e as the carriage 4S is moved rearwardly.

Whenever the pens 4u are driven, -a multiple point ca-m 84 axially secured to shaft 46h :is also rot-ated to `actuate a `switch S6 at each point. The cam 'Se preferably has a number of points 84a corresponding to the number of pens 40. The switch 6 has, for example, a grounded pole so that as the pole is actuated 'by the cam points 34a, a ground (positive relative to a negative supply) pulse is produced each time which is used in a control circuit to regulate the speed of the motor '7o. The cam S4 is positioned with respect to the pens 4t) such that a ground (positive) pulse is produced whenever a pen has swept across the paper 36 and reaches a certain position in its travel along the recording paper. The pens riti are always driven at least at a relatively slow idling speed. It is noted that the pens di) are equally spaced about the band 42, and the points `Sdu are correspondingly equally spaced about the periphery of the cam S4. The cam 84 and associated switch Sti can, of course, be mounted to be driven and operated olf the shaft 46a.

FIGURE 3 sho-ws a schematic block diagram of our invention. The microphone 3,-@ can be held against the chest lover the heart of a patient and the electrical signal output thereof is fed to a preamplifier 8S. The output of the preamplifier Sd is, in turn, fed to an automatic gain ycontrolled amplifier 9i). Automatic gain control serves to keep the `average level of all signals constant in order to compensate for variations in microphone positioning and thicknesses of the chest wall of different patients. The preamplifier 88 and the automatic gain controlled amplifier 90 lare conventional devices and need not be shown in detail.

The output of the amplifier 9d is provided to a modulator 92 and to a synchronizing signal filter 94. The output of the amplier 90 can also be Iapplied to a power amplifier 96 which drives a speaker 98 on closing of a switch 1&0. The output of the amplifier 96 can also be applied to headphone 32 by closing a switch 102.

Heterodyne oscillator 104 provides a variable frequency signal which is 1combined with the output signal of amplifier 9i) -by the modulator 92. The frequency of lthe oscillator signal is varied by a suitable coupling means ldd which is actuated by movement of carriage 45B (FIGURE l) laterally with respect to the paper 3d and mechanically controls the adjustment of 4the oscillator 1M. The frequency of the oscillator signal is progressively decreased from a first predetermined maximum frequency to beat with the low end yof a selected frequency range to a second predetermined minimum frequency thereof to beat with the high end, corresponding respectively with the limits Aof forward and rearward travel of the carriage 45.

The modulated output signal from the modula-tor 92 is a combination of the original (amplified) signals and the sum and difference beats of the yoriginal (amplified) lsignals and the `frequency of oscillator 1M. Filtering is obtained by the intermediate frequency (-I-F) amplier which is tuned to a fixed frequency that is higher than :any of the heart sound signals. The -F amplifier responds only to signals at a frequency which will add to the oscillator frequency to equal the fixed intermediate frequency.

As the oscillator 164 is progressively tuned to a lower frequency by gradual motion of the carriage 48, laterally over the surface of the paper .36, it beats with progressively higher signal frequencies of the original (amplified) signals to produce a frequency equal to the I-F frequency. This system acts as a selective filter which can be tuned through the range of heart sound frequencies in accordance with lateral motion of the carriage 4S. Output of the I-F amplier is coupled to pen-write circuitry 11d.

The circuitry 11d electrically energizes the band 42. which can be made of suitably conducting material such that the pens 4h will produce markings on the paper 36 while contacting the surface thereof, `as indicated for the pen 40C. The pen-write circuitry 114i operates whenever an input signal thereto exceeds a preset, predetermined minimum level.

The motor 68 has a field 68a which is energized by 28 volts as indicated in FGURE 3. The motor d8 is shown mechanically connected to the coupling means 106 to drive the carriage 4S and vary the frequency of the output signal of the oscillator 104. Movement of the carriage 48, of course, also actuates the arm Ida of switch 78 between the contacts 731'; and 73o. As shown, the arm 78a is connected to 28 volts, and the contact 7d-b is connected to ground through the control coil Stia of the relay Sti.

The relay 8@ has three two-position poles glib, 80C and Stir! which are respectively associated with three pairs of contacts diie and if, tig and duh, and 8th' and 80]'. The contacts Stic and Slik are both connected to one side of the armature of the motor ed, and the contacts Stif and Eidg are both connected to the other side of the armature. The pole Sub is connected to 28 volts, and pole Stic is connected to ground as shown. Thus, the motor 68 will be energized to rotate in one direction when the relay Si? is not energized, and will rotate in another direction when the relay d@ is energized.

The relay contact j is connected to one side of the armature of motor 76, and the other side of which armature is grounded. The pole Stift is connected to the output of a power pulse circuit 112 having an input connected to 28 volts, The -28 volts is also connected to energize the field 76a of the motor 76. The output of the power pulse circuit 112 will energize the motor 76 when the relay S9 is not energized.

As indicated in FIGURE 3, the output of the armature of the motor '75 is mechanically connected to drive the pulley 44a and the multiple pointed cam 84. Thus, the band 42 and hence the pens 40 are not driven when the switch arm 78a of the switch 78 engages its contact '7817 and energizes the relay coil Sua. Accordingly, the -band 42 and the pens dit are stopped while the motor 68 is reversed in direction of rotation to return the carriage 48 back to its forward limit position and power turned off to stop the machine if another pattern recording is not desired.

The output synchronizing signals from the filter 94 are used to turn on or trigger the artificial heart beat generator 114, which is a conventional bistable multivibrator circuit. This multivibrator is turned off or reset by closure of switch 86 which is actuated by cam 84. Each synchronizing pulse turns on generator 114 and it remains on until the pen drive mechanism travels to the point where switch S6 is actuated. This produces variable width output pulses which are amplified by the power pulse amplifier 112 and used to control and synchronize the speed of the motor 76.

The power pulse amplifier 112 also provides, through a suitable resistor (R5 in FIGURE 9), a constant idling or minimum power to the motor 76. This reduces the amount of controlled power needed for changing motor.

speed over the range desired.

The power pulse circuit 112 normally provides a constant idling power to the motor 76, which idling power is increased by variable width power pulses controlled by signals from the generator 114 to produce variable width power pulses which are applied to the armature of the motor 76.

annesse The leading edge of an output pulse from generator 114 establishes and coincides with the leading edge of a corresponding power pulse from circuit 112. However, the pulse widths of the output pulses from the generator 114 are controlled by switch 86 which is actuated by the cam 84 to terminate or establish the trailing edge of an output pulse from the generator 114. The cam 84 is, of course, mechanically coupled to the output of the motor 76 and is a measure of the position of the pens 4t) relative to a reference position on the surface of the paper 36. This requires, of course, that there be no slippage between the drive pulley 44a and band 42. Y Switch 86 is operated to establish the pulse width of each output pulse from the motor pulse generator 114. In this way, the speed of the pens 40 is synchronized with the pulse rate from the filter 94 so that a constant distance is covered by each pen for various pulse rates over a selected range. For example, at some particular rate of output pulses from the filter 94the motor 76 and the pens 4t) will be driven at a certain corresponding speed. If the rate of the output pulses from the filter 94 should increase, the output pulses from the generator 114 will also increase in rate. The rate of the power pulses from circuit 112 is thus similarly increased. This will start each power pulse sooner.

Since the cam 84 must be driven by motor 75 a certain distance before the switch 36 is actuated, and a corresponding output pulse from the generator 114 is terminated with each actuation of the switch 86, the speed of rthe motor 76 will be increased because the average power provided thereto will be greater over each cycle of the higher frequency signals now appearing from the circuit 112. The net result is that the increase in speed of the motor 76 drives each of the pens 40 over approximately the same distance at the new frequency as it did originally.

Similarly, should the rate of the output pulses from the filter 94 become slower, the rate of the output pulses from the generator 114 is also decreased such that less frequent power pulses will be supplied to the motor 76. This will start each power pulse later. Since the cam 84 must be driven by the motor '76 a certain fixed amount before the switch S6 is operated to terminate an voutput pulse from the generator 114 and hence the corresponding power pulse from circuit 112, the average power provided to the motor '76 is decreased. Thus, the pens 4@ are driven at a slower speed to cover the same distance on paper 36 for output signals from the filter 94 of a lower rate than before. Correct speed for the motor '76 and pens 40 are maintained over a relatively wide predetermined range of frequency or pulse rate variations to produce charts of the same, uniform size.

idling power alone provided to the motor '76 produces a minimum pen speed on paper 36 corresponding to a minimum rate output signal from l'ilter 94, and idling power plus a power pulse which has a width covering the full cycle of the output signal from generator 11o' produces a proper pen speed corresponding-to a maximum rate output signal from filter 94. Thus, more frequent pulses, at an increasing width power pulse for each cycle of the output signal from filter 94 are added to the idling power to motor '76 for an increasing frequency of the output signal from filter 94.

Since the pens 4@ are driven at a speed which is variable the rate of a variable rate Vsynchronizing signal, pulse rate marker 118 is provided to record this information by producing marks (118g and 11811 in FIGURE 10) on the paper 36 in response to the beginning of each output pulse signal from the articialheart beat generator 114.

The pulse rate marker 118 can be a conventional differentiator circuit which produces a narrow pulse from the leading edge of each output pulse from the generator 114. The narrow pulses are applied to the pen-write circuitry 11i), causinga very short line to be drawn on the record paper. These small periodic marks on the paper 36 indicate the pen speed which is directly related to the d repetition rate of the output signals from the filter 94. This gives a record of the patients heart rate and also shows any changes of rate that occur during a test. Details of the conventional differentiator circuitry of the pulse rate marker 118 are not shown.

FIGURE 4 shows a preferred circuit for the modulator 92. As can be seen, the modulator circuit includes a transistor Q1 connected in an emitter follower circuit having an input connected to the output of the automatic gain controlled amplifier 90 and an output connected to the primary winding of a transformer T1. The secondary Y of the winding of the transformer T1 is connected to ends of a balance control potentiometer R1 through respective, negatively oriented diodes CR1 and CRZ which are, for example, type IN462 diodes. The anodes of the diodes of CR1 and CRZ are connected to respective ends of the primary winding of the transformer T2 and the secondary winding of the transformer T2 is connected to the intermediate frequency amplifier 1%.

The output signal from oscillator 104 is applied to the primary winding of a transformer T3. One end of the secondary winding of the transformer T3 is connected to the center tap of the secondary winding of T1, and the other end of secondary of transformer T3 is connected to ground as shown. Thus, as is apparent from FlGURE 4, a modulating frequency signal is applied between the centers of a bridge circuit, and a modulated output signal is obtained across the ends thereof. Modulation or cornbination is accomplished in the arms of the bridge circuit including respective halves of the secondary winding of the transformer T1, and diodes CE1 and CRE.

FTGURE 5 shows a preferred circuit for the oscillator 194. The transistors Q2, Q3, and Q4 are connected in respective common emitter amplifier circuits, and the transistor Q5 is connected in an emitter follower circuit. Feedback network 12@ connects the output of the transistor Q4 back to the input of the transistor Q2. This feedback network 12d includes parallel branches of a bridged-T filter network 122 and a pi filter network 124.

The pi filter network 124 includes a tuning control potentiometer RZ having an adjustable wiper which Vis mechanically varied 'by the coupling means 1516 in accordance to the movement of the carriage 48. Thus, the output frequency from the oscillator 194 is varied with movement of the carriage 48.

Gain control is effected by a series network including a negative resistance element R3 and capacitor C1. The oscillator 104 is a tuned oscillator circuit which is variable in frequency from, for example, 2,000 to 3,200 cycles per second (cps). The output of the oscillator 104 is applied to the primary winding of the transformer T3 shown in FIGURE 4.

FIGURE 6 illustrates a preferred circuit ofthe intermediate frequency amplifier' 108. The amplifier 1118 is a fixed frequency amplifier having a 2,000,c.p.s. resonant tank including inductor L1 and capacitor C2 located at the input thereof, The amplifier 1118, as shown, has four stages of amplication which include the transistors Q6, Q7, Q8 and Q9 connected inV generally conventional circuitry. The output of the intermediate frequency amplifier 1% is connected to the input of the pen-Write circuitry 111B.

FIGURE 7 shows a preferred circuit diagram of the pen-write circuitry 11th. The output of the intermediate frequency amplifier 1% is applied to the transistor Q10 connected in an emitter follower circuit which has its output connected to the gate electrode of a controlled rectitier CRS. As is well known, when a sufficient voltage is applied between the gate and cathode electrodes of the controlled rectifier CRS, the controlled rectifier is fired when its anode is positive a necessary amount relative to the cathode. Firing of the controlled rectier CRS thus energizes the pen 126. Poweris supplied by means of the transformer T4 having, for example, 115 volts, 60 c.p.s. power applied to the primary winding thereof.

Once the controlled rectier CRS is fired it remains so until the anode voltage drops to zero or becomes negative with respect to its cathode. Thus, the pen 126 can become energized only during the positive half cycles of the 60 c.p.s. signal applied to the transformer T4. This frequency is sufficiently high enough, however, that the electrical marking action of the pen 12d appears to be continuous during the time that the pen is energized any length of time.

FIGURE 8 shows a preferred circuit for the synchronizing signal filter 94. The output from the automatic gain controlled amplifier 9i) is supplied to the input of the synchronizing signal filter 94 and the output from the filter 94 is connected to the artificial heart beat generator 114. As can be seen in FlGURE 8, the filter 94 comprises two transistors Q11 and Q12 connected in two arnplier stages having a feedback network including a variable resistor Re and a parallel capacitor C3 connecting the emitters of the transistors Q11 and Q12 together. Circuit elements are chosen to select an output signal of a particular frequency which will establish a desired synchronizing signal. The synchronizing signal is normally that of a predominant beat sound of a heart, for example. The variable resistance R4 can be adjusted for different predominant sounds or frequencies of different persons, to cover a variety of sounds and pulse rates.

FIGURE 9 shows a preferred circuit for the artificial heart beat generator 114 and the power pulse circuit 112. The output from the synchronizing signal lter 94 is supplied to the input of the artificial heart beat generator 11d and the output of the generator 114 is suitably filtered and used to control the power pulse output of the circuit 112. The generator 114 preferably comprises two transistors Q13 and Q14 connected in a substantially conventional bistable multivibrator circuit.

The output signal from the artificial heart beat generator 114 energizes the cascaded transistors Q15 and Q16 such that an increased power pulse is provided from the circuit 112. Normally, when the transistors Q15 and Q16 are not conducting, idling power is provided through the shunting resistor RS to the output of the circuit 112. The output from the power pulse circuit 112 is provided to the armature of the motor 76 when the relay Sti is not energized such that the relay pole 80d engages its Contact 80]' (FIGURE 3). rThe power pulses from the circuit 112 are varied in width such that the motor '76 is driven at a proper speed when it is energized.

As mentioned previously, the motor 76 is driven by power pulse circuit 112 which ampliiies the pulses from artificial heart beat generator 114. Pulse generation is initiated by the output from the synchronizing signal lter 94 which triggers the transistor Q13 (FIGURE 9). The termination of each power pulse is controlled by switch 86 which is actuated by cam 34 causing a pulse to be applied to transistor Q14. This resets the multivibrator circuit of generator 114. The net effect is that if the pens 4l? are moving too fast, cam S4 will be actuated sooner and cut the power pulse short. If the pens itl are moving too slowly, there will be a slight delay before the cam 84 shuts off the power pulse to the motor. This longer pulse of power will speed up the pen motion to correct the speed and also automaticaliy index the pen location tothe same longitudinal position on the paper 36 for each part of one heart beat.

The net eect is that the output pulses from the power puise circuit 112 will be varied in pulse width according to the .pulse rate output of the heart beat generator 11d such that the motor 76 is driven at a variable speed to produce a substantially-constant travel distance for each of the pens d@ on paper 3d for all frequencies or pulse rates of the output signal from the synchronizing signal filter 94 over a wide frequency or pulse rate'range.

FIGURE l0 is a drawing showing a section 12S of the paper 36 having a pattern produced thereon by the stethoscopic spectrograph. The section 123 horizontally covers the time interval over, for example, two complete cycles of the synchronizing signal from the filter 94 (FIGURE 3). Vertically, the plot covers a frequency range from, for example, 25 c.p.s. to 1600 c.p.s. The pens 40 each make a horizontal sweep across the section 123 in rapid succession as the carriage 48 is moved in a lateral (vertical in FIGURE l0) direction together with a progressive variation in frequency ofthe output signal from the oscillator 11M. The coupling means 1115 is such that it varies the frequency of the oscillator 16M very slowly in comparison with the horizontal sweep velocity of each sweep of the pens ill over the section 12S of the paper 36. Of course, it -is possible to provide coupling means 106 of the nature which has an eccentric action that adjusts the frequency of the oscillator 11M quickly at the end of a sweep with little, if any, adjustment during the main sweep portion thereof. ln this way, signal components of a substantially constant frequency are plotted on paper 36 during each sweep.

The spectrograph pattern over the rst half of the section 12S shown in FTGURE l0 is similar to that of the second half of the section 128. By recording two substantially similar patterns over the section 128 of the paper 36, it is always possible to obtain a complete pattern over one full cycle of the input signal throughout the frequency range under consideration irrespective of what point is chosen as a reference. As can be Seen from FIGURE 10, the pattern including the formations A1, A2, A3, B1 and B2 are duplicated over the section 128 by the pattern including the formations A1a, AZa, A351, Bla and B251. This assumes, of course, that the input signal to the stethoscopic spectrograph is not radically varied during the time that the patterns shown in FTGURE l0 are being recorded over the section 12S of the paper 36. If radical variation does occur, it is desirable that the recording shows it.

It is noted that certain types of heart sounds normally appear at some corresponding time of each cycle of a heart signal. These sounds result in frequency components being plotted in certain formations in accordance with the frequency selection caused by tuning of the oscillator 11M. Thus, over one cycle of a substantially uniformly repeating heart signal, a composite picture of the various frequency components with respect to the time of one period is obtained. Accordingly, if certain, normal, high frequency components of an input signal are missing from, say, the latter half of a pattern, this would indicate that a certain valve of the heart is functioning improperly. While the input signal to the spectrograph is usually that of a patients heartbeat, other similar signals can be recorded and any trouble can be determined by proper analysis of the recorded pattern.

An important feature of the invention is that the patterns are recorded by lines of uniform density. There are no shadings from dark to light as found in cathode ray oscillograph recordings. This allows the patterns to be photographed or otherwise duplicated without loss of information. The relative intensity of the individual sounds recorded is shown by the vertical width of the pattern. For example, a Weak 300 c.pS. sound may be recorded for the interval during which the filter is tuning from 295 to 305 c.p.s. A stronger 300 c.p.s. sound might be heard from 250 `to 350 c.p.s.

Only sounds which exceed a pre-set minimum value are able to trigger the pen-write circuitry. If this threshold value is set too high, only a few small areas will be recorded. If the threshold is set too low, there will be so many sounds recorded, with each sound covering a large area, that it will be diiiicult to identify individual sounds.

The ability of the instrument -to select signals which exceed a pre-set level is dependent upon the amplilier 9i) which incorporates automatic gain control circuitry. Regardless of the positioning of the microphone 30 or transmission of sound vibrations through the chest walls of anar-reas different patients, the amplifier 90 output is constant. This constant output consists of all the sound signals. The automatic gain control circuitry keeps the total of all signals at one level. Subsequent ltering hy the modulator 92 and I-F stages of amplier 108 then shows the individual sounds and a comparison of the relative strength of each signal.

This is similar tothe action of A.G.C. circuits in radio receivers. The listener adjusts the volume control for the average sound level desired. Then all broadcast station programs will sound equally loud, but individual sounds will vary in loudness. In our spectrograph, the effect is that an -equal amount of ink, (or pattern area marked), will be used even though a pattern is radically different from a previous recording.

The pen-write circuitry 110, shown in FIGURE 7, is only able to hear the sounds, one at a time, as the lilter is tuned through the sound range. This is comparable to tuning an audio lter through the sounds heard on one broadcast station. When the pen-write circuitry 110 receives a sound signal large enough to overcome the negative bias on thet gate electrode of CRS (FGURE 7) the pens lil are activated. The pen will stop writing if thesignal level falls below the threshold level. This is because the anode of CRS is suppied by :alternating voltage. It stops conducting on the negative half of each cycle and -must be yire-triggered by the signal when the anode swings positive again.

Another particularly important feature of our invention is the fact that the moving ypens 40 are synchronized with a patients heart beats. The pens 40 move atv a speed which corresponds to the heart rate, so that a pen will traverse one-half of the, for example, 10 inches long recording pattern area on paper 36 once for each beat. In addition, the pen position is automatically indexed to a particular heart sound which occurs once during each beat. By locking onto one particular synchronizing signal, the pen control drive holds the pens 40 in phase with the sequence of sounds of each heart beat. A pen is always traveling through the same horizontal (longitudinal) zone of the recorded pattern when any particular sound recurs.

Control of the motor speed and indexing of the pen position is done by varying the repetition rate and duration of power pulses which drive the motor 76. A small amount of continuous power is also fed to the motor 76.

The motor pulse repetition rate is automatically adjusted to match the heart rate. Indexing of the pen position so it stays in phase with the sequence of sounds within one heart beat is done mechanically. Every time a pen passes one point it triggers `a switch 86 which terminates the power pulse tothe motor 76.

A motor power pulse is started when the synchronizing signal occurs. This signal is a sound which happens once during each heart beat. The pulse is stopped when the pen has traveled to the switch 86.

In normal operation, when plotting a pattern, the pen will sweep halfway across the pattern before the synchronizing signal turns on a power pulse. When the pen reaches the end of the pattern, the switch S6 turns off the power pulse. The motor 76 is thus powered half the time, or for a duty cycle.

When the instrument is rst turned on, a synchronizing pulse turns on power to the motor 7e. As a pen itl starts moving slowly, other synchronizing pulses occur but have no effect because power is still on. When the pen finally reaches the switch S6, power is turned off. Because the pen is still moving slowly, it is Y hardly started across the pattern again before another synchronizing signal puts motor power back on. The duty cycle of motor power approaches 100% when the instrument starts.

If the instrument is plotting a pattern and the patients heart rate slows, the pen speed will automatically slow and stay in synchronisim. Since the pen speed was effective'ly too fast, a pen d@ will rush past the usual halfway point before a synchronizing signal starts a new motor pulse. This shortens the distance and time to the stop switch 85, resulting in a shorter power pulse to the motor 76. When the pen must slow down to stay synchronized, the duty cycle of motor power pulses becomes less than 50%.

FIGURE 11 shows how the motor power duty cycle varies with motor pen drive speed. When first started, theduty cycle is almost The duty cycle drops to 33% when speed is 40% greater than synchronous speed.

When the motor speed has increased to where it appreaches synchronous speed, the duty cycle is determined by the phase relationship of the synchronizingV signals and proximity of the pens 450 to the cut-olf switch 86. A further speed increase shortens the instantaneous distance between the pens and cut-olf switch. This slows the motor 76 because its duty cycle approaches zero. Slowing the motor 7o causes it to slip in phase until the duty cycle is sulicient to Vmaintain synchronous speed. The pen speed is then synchronized with the `heart rate and pen positionv is in phase with the synchronizing signals.

The char-t of FIGURE L1l diagnammatically illustrates and explains the automatic 'operation of the pen m'otor Vsynchronizing principle 1o'f our invention. As indicated in this figure, horizontal Kdistance' from the ordinate axis of the chart represents icyclic pen travel in, for example, inches. Pen travel is plotted ttor vtarious pen speeds. Activation lof the switch 36 hy the earn 84 (FIGURE 3) for each point of ythe calm S4 is indicated in FIGURE 11 by stop-switch markings (x) provided .at equal 5 inches .of pen travel intervals lon the graph of FIGURE 11.

Each pen 40 travels 10 inches on paper 36 for each sweep. The hlatched .markings |made on the different pen speed plots of the .graph represent the production or appearance lof an output pulse from the power pulse circuit 112. Each power pulse is, of course, terminated by an actuation ofthe stop-switch 86.

For purposes of illustration, a dominant signal frequency or pulse rate of 60 cps. has heen lassumed in making IJthe graph `of FIGURE 11. The small heart shaped markings indicate the appearance `of each trigger pulse from the artificial heart heart generator 114 (FIG- URE 3). These heart shaped markings therefore indicate the beginning [of van output pulse from the power pulse circuit 112. Synchronized pen speed is shown as 5 inches per second :for the assu-med dominant heant frequency or pulse rate of 5 inches per second. Substantially constant pen speed -is produced Iand maintained hy the power pulses.

The hatched mlarldings lfor pen speeds of 1 to 7 inches per sec'ond illustrate the variations of power pulses from circuit `11.12 at the respective pen speeds over a complete cycle of yoperation for `all of the three pens 40. The second lower row of hatched markings art the pen speeds of 4.5 and 7 inches per second illustrate a respective following 'cycle of -oiperaltion showing the continued variation of power pulses in response to the appearance of the trigger pulses from the artificial heart heat generator i114.

Where the pen speed is less than the synchronized pen speed of 5 inches per second, the power pulses produced in response no each output pulse from the artiicial heart lbeat genenator 114 at the assumed dominant frequency or pulse rate of 60 cps. are generally not unifonmly spaced or of equal duration over a complete cycle of operation. This is indicated by the irregular, hatched markings on the 1, 2, 3, 4, 4.5 and 4.99 inches per second p plots. The pens 40 will accordingly he driven at a progressively increasing speed until the synchnonized pen speed of 5 inches per second is achieved.

As can be seen `fnom the graph of FIGURE 11, the regular and uniform, hatched markings for la pen speed of 1 inch per second show that over a complete repetitive cycle of operation, the motor 76 is supplied with a power pulse from the power pulse circuit 112 at least 80% of a sweep cycle. The duty cycle of motor 76 with respect to being driven |by .a power pulse averages 70% for a pen speed of 2 inches .per second. As the pen speed increases towards the correct synchronized pen speed of 5 inches per second, the average motor duty cycle (with power pulses) pnogressively drops as fthe power pulses are averaged over an increasingly greater number of pen travel intervals. It can be seen from the plot for pen Speed of 4.5 inches per second, power pulses are widely varied in duration over nine 5 inch pen tnavel intervals before repeating tits cycle. The average is increasingly spread so that the motor 76 slow down as the pens 40 approach synchnonized speed. This 'effect is accentuated by the fact that the motor 76 requires more power at higher speeds.

The motor 76 will drive the pen-s 4G fat synchronized speed which rior the illustrative graph of FIGURE 11 may be approximately 5 inches per second after this speed is reached. The pens 40 are maintained at synchronized speed because any tendency for the motor 76 to slow down would :be opposed by increasing power .pulses thereto. However, a certain amount of power pulses is necessary to maintain correct sychronized speed. This is accomplished once synchronized speed is attained, in the process lof Iachieving Ia steady state condition. The lack of power pulses at synchronized speed induces the motor 76 to slow but which results in producing power pulses thereto, causing a transient hunting .period during which the motor 76 elfec'tively slips in phase until a correct amount of power pulse is uniformly applied during every cycle of heart beat such that synchron'ized pen speed will be maintained. Irf the motor 76 tries t-o accelerate through the synchronized pen speed of 5 inches per second, ttor example, it will automatically approach zero added power .pulse and slip back. The flywheel etect provided by the pulleys 44a and 44h will prevent the motor 7 6 from jumping through synchronized speed, and maintain a steady state condition.

'If the motor 76 should drive the pens 40 too fast, the average power pulse for each 5 inch interval over a repetitive sequence of power pulses is significantly decreased by the appearance of intervals without any power pulse at all. As can be seen in FIGURE 11, the plot for a pen speed of 6 inches per second has two such empty intervals, and the plot for a pen speed of 7 inches per second has three such empty intervals over respective repetitive sequences of power pulses. Signiiicant speed increases are therefore not prevented but yet any overspeed of the pens 40 is soon reduced and brought back to synchronized speed.

A modified version of our invention is shown in FIG- URE 12. This modiiied version of the invention ernploys a stepper motor drive that results in a somewhat simpler instrument. As can be seen in FIGURE 12, the power pulse circuit 112, and cam 84 and switch 86 are not used. A pulse generator 130 which can be manually preset to a patients approximate heart beat repetition rate is used instead to provide power pulses to a stepper motor 132 that is connected todrive pulley 44a. Control of the stepper motor 132 is obtained through use of relay 134.

The artificial heart beat generator 1145i is a one-shot multivibrator having a relatively narrow output pulse which is produced in response to an input trigger pulse thereto. This generator 114'a'differs from the generator 114 of FIGURE 3 in that it is not a bistable multivibrator using an output pulse length control connection. The output of the generator 114e is suitably applied to the relay coil 134a. When the relay coil 134e is energized, the poles 134b and 134e of the relay 134 are actuated such that the pole 134k connects +28 volts to the coil A134e to lock the relay, and the pole 134e connects the 1li output of the pulse generator to the stepper motor 132. Carriage 4S and oscillator 104 are controlled as before.

Mechanical switch 136 is driven by the pulley 44a, and has a rotating arm which is connected to ground and a contact that is connected to the relay coil 134a through a capacitor C4. The capacitor C4 is shunted by an energy absorbing resistor R6. The switch 136 is utilized instead of the cam 84 and switch 86 of FIGURE 3. When the switch 136 is closed after a pen has made its plot on the paper 36, the capacitor C4 acts to short the relay coil 134a momentarily to (le-energize the lookup circuit by releasing the pole 134b.

In operation, the pulse generator 130 is preset according to the patients approximate heart rate. The patients approximate heart rate is first measured, and then the knob 130s is set on the corresponding marking on the calibrated dial 130b. This produces output pulses from the generator 134) of a frequency which drives the stepper motor 132 at a constant speed that causes a pen (such as pen A) to sweep over the paper 36 a predetermined distance for each cycle of the heart signal. This predetermined distance is, of course, the same when the knob 134m is correctly set against dial 13017 for other heart rates over the entire range of the calibrated dial 13d/5. The diameter of the pulley 44a is such that one complete revolution thereof will move the pen A from the beginning of a recording section of the paper 36 to a point at the end of the section, at which time the pen B is then positioned at the beginning of the section.

Three synchronizing signals per sweep of a pen are used. At the start of the first synchronizing pulse from the generator 114m, the relay 134- is energized and the stepper motor 132 is driven by the output of the pulse generator 13) at the constant preset speed. The stepper motor 132 is driven at a speed wherein two heart cycles and a fraction are plotted on the paper before the mechanical switch 136 is closed to de-energize the relay 134. Since more than a complete heart cycle is plotted on the paper 36, the output pulses from the pulse generator 13) need not drive the stepper motor in exact proportion with the patients heart rate. After the relay 134 is de-energized, the next trigger pulse from generator 114e will be effective to energize the relay 134 and start another cycle of operation. Generator 130 is turned off on carriage 48 return. Instead of a stepper motor, a synchronous motor can, of course, be used. A variable output speed can be obtained by using adjustable gearing means, 4for example, which can be preset to produce an appropriate output speed therefrom according to the measured approximate heart rate of a patient. The output of the gearing means is then used to drive the pulley 44a through suitable coupling means such as a magnetic clutch controlled by a relay similar to relay 134. A magnetic clutch is preferably used to provide rapid coupling and de-coupling of the adjustable output of the gearing means to the pen drive mechanism.

FIGURE 13 shows another version of our invention which is structurally simplified still further. The carriage 48 has been eliminated and only a single motor is used for driving the pens et) and paper 36. Motor 137 drives a worm 138 which engages a worm gear 140 mounting pulleys 142 andv144 on respective ends of gear shaft 146. The pulley 144 is connected to a similar pulley 148 through an endless band 150. The pulley V168 is rotatably mounted, and is rotated with movement of the band 150 through tensional friction between the band 150 and the rim of the pulley 148. The band 150 is electrically conductive and mounts pens 40.

The pens 40a, 4019 and 4de are mounted equally spaced on the band 150, and sequentially engages the surface of the paper 36 which is electrically marked by the pens 40. The pulley 14S is electrically conductive and is suitably connected to the common junction between the secondary winding of transformer T4 and its series capacitor as shown in FIGURE 7. The pulleys 144 and 148 are positioned as shown in FIGURE 13 so that the pens 40 are driven in a plane which is perpendicular to the surface of the paper 36 over the vacuum platen 38. The platen 38 also serves as a ground plane which is connected to the other end of the aforementioned capacitor of FIGURE 7.

The pulley 144 is not electrically conductive like the pulley 148. However, mounted to rotate with the pulley 144 on the shaft 146 is a two-point cam 152 which is suitably connected to ground. The ends of the cam 152 engages a contact element 154 which is connected to the artificial heart beat generator 114. The cam 152 therefore corresponds to the switch 36 of FIGURE 3. The pulleys 144 and 148 are, of course, constructed to provide a suitable flywheel effect.

The pulley 142 drives a larger pulley 156 through a connecting belt 158. The pulley 156 drives a worm 16@ which meshes with a worm gear 162. Rotation of the worm gear 162 drives a sprocket wheel 164 mounted on one end of shaft 166, and a cam 168 and the wiper of a potentiometer R2a mounted on the other end thereof. The sprockets of the wheel 164 engage the holes in the paper 36 to drive the same, and the cam 168 operates a stop switch 170 once each revolution. The potentiometer R2a. is a 360 degrees continuous rotation device and corresponds to the potentiometer R2 shown in FIG- URE 5.

The paper 36 in FIGURE 13 has an effective writing width of inches, and the pulleys 144 and 14S are suitably spaced so that the pens 40 will contact the surface of the paper 36 this distance for each sweep of a pen 4i). The pulleys 144 and 148 preferably are spaced 10 inches apart, and have 10 inch effective circumferences for engaging the band d. Dimensions of the components are such that shaft 146 is driven at 30 rpm., pulley 156 at l0 rpm. and shaft 166 at 1A r.p.m. The sprocket wheel 164 has a root diameter of 1.272 inch, for example.

FIGURE 14 shows a circuit diagram for the version of our invention shown in FIGURE 13. The circuit of FIGURE 14 is fragmentary in that the rest of the circuit which is not shown is the same as certain parts of the circuit of FIGURE 3. The relay 80 in FIGURE 3 is not needed since a movable carriage is not used and, of course, motors 68 and 76 have been replaced by a single motor 137. Cam 152 and contact element 154 corresponds to switch 86, as mentioned above. The circuit of FIGURE 14 includes a stop switch 170 actuated by cam 168, and a start pushbutton switch 172 which are not used in the circuit of FIGURE 3. Other than the circuit connections shown in FIGURE 14, the remainder of the circuit can be the same as that of FIGURE 3.

By having a single motor 137 driving both pens 40 and paper 36, recording patterns are produced which differ from those made by the machine shown in FIGURES 1, 2 and 3 in that the parallel spacing between marks made by the pens 40 would be uniformly spaced on various successive sweeps since greater pen speed would result in greater paper speed. Thus, the faster that the pens 40 are driven, the faster will the paper 36 be moved at right angles thereto, as can be easily seen in FIGURE 13. This means that for persons having different heart rates, their respective records in the usual steady `state conditions, would Yproduce records on paper areas covering the same width and length.

Operation of the version of our invention shown in FIGURES 13 and 14 is virtually automatic in producing a pattern recording. Closure of the power switch 174 in FIGURE 14 supplies power to the various circuits. Depressing the start pushbutton switch 172 momentarily will energize the motor 137 which drives cam 168, the wiper of potentiometer R2a, cam 152, paper drive sprocket Wheel 164 and pen drive pulley 144. Cam 168 is contoured to cause switch 170 to close and shunt start switch 172 in order to continue supplying power casse (idling power and power pulses) to motor 137 after switch 172 is released. Variation of the resistance of potentiometer RZa will vary the output yfrequency* of oscillator 164m which is similar to the oscillator 104 shown in FIGURE 5. Cam 152 functions asa switch with the contact element 154 to control the length of the power pulses from the circuit 112 in the same manner as the switch 86 in FIGURE 3. Y v

After a complete pattern is recorded on the paper 36, the stop switch 170 is actuated (opened) by cam 168 which has then made yone complete rotation. This removespower from motor 137 and stops further recording. vThe wiper of the potentiometer R2@ has also made va complete revolution. `If another yrecording pattern is desired, the pushbutton switch 172 can be depressed again. Once motor 137 is started on a recording cycle, emergency stopsV must be made by opening power Switch 174.

It should be apparent from the foregoing description that the particular versions or embodiments of our 1nvention described above and shown in the drawings are exemplary of, and not restrictive on, our broad invention, and that various changes in design, structure and arrangement may be made in the invention without departing from the legitimate and valid scope of the appended claims.

We claim:

1. A stethoscopic spectrograph, comprising:

recording material having a surface adapted marked;

means for moving said recording material over a re cording platen in a first direction;

pen means movable in a second direction at substantially right angles to the first direction, said pen means being energizable to mark the surface of said recording material;

microphone means adapted to pick up generally periodic sounds and convert the same into electrical signals; means for moving said recording material and said pen means at first and second speeds, respectively;

means coupled with said moving means and adjustably varied thereby for detecting different frequency components of the electrical signals and energizing said pen means therewith; and

means for varying movement speed of said pen means in response to the periodic rate of a predominant sound of the periodic sounds picked up by said microphone means, so that said pen means is moved substantially equal distances over respective periods of different periodic rates of the predominant sound of the periodic sounds whereby recordings of uniform size are produced over a wide range of different periodic rates of the predominant sound of the periodic sounds.

2. The invention as defined in claim 1 wherein said pen means includes a plurality of energizable pens which are mounted in spaced relationship` on an endless band, said band being driven by said moving means whereby said pens are moved at the second speed with respect to the surface of said recording material.

to be .3. The invention as defined in claim 1 wherein said signals from said/microphone means whereby the combined signals can be adapted to energize said pen means. 4. The invention as defined in claim 1 wherein said moving means is adapted to drive said recording material and pen means at respective first and second speeds which are proportional toeach other.

5. The invention as defined in claim 1 wherein said means for varying movement speed of said pen means includes filter means for obtaining Aa predominant sound signal of the periodic sounds, means for applying a power signal to said means for moving said pen means in the second direction in response to the predominant sound signal, and means connectably driven with `said pen means for stopping said power signal at a predetermined position of said pen means in the second direction with respect to the surface of the recording material whereby the power signal is reduced in average duration when the periodic rate of the predominant sound signal is low and increased in average duration when the periodic rate of the predominant sound signal is high.

6. The invention as defined in claim r1 including means responsive to a predominant sound signal of said periodic sounds to energize said pen means and produce a rate marking on said recording material for each cycle of the predominant sound signal.

7. A stethoscopic spectrograph, comprising:

recording material having a surface adapted to be marked; means for positioning a section of said recording material on a recording platen;

carriage means movable along a first axis with respect to the surface of said recording material;

pen means movably mounted to said carriage means and movable along a second axis which is substantially at right angles to the first axis, said pen means being energizable to mark the surface of said recording material;

microphone rmeans adapted to pick up generally periodic sounds and convert the same into electrical signals;

means adjustably coupled with said carriage means and responsive to movement thereof in a predetermined direction along the first axis, for detecting different frequency components of the electrical signals and energizing said pen means therewith;

means for driving said carriage means in the predetermined direction along the first axis with respect to Vthe surface of said recording material;

means for driving said pen means with respect to the surface of said recording material; and

means for varying movement speed of said pen means in response to the periodic rate of a predominant sound of the periodic sounds picked up by said microphone means, so that said pen means is moved substantially equal distances over respective periods of different periodic rates of the predominant sound of the periodic sounds whereby recordings of uniform size are produced over a wide range of different periodic rates of the predominant sound of the periodic sounds.

8. The invention as defined in claim 7 wherein said recording material includes paper having a treated surface for producing visible markings thereon when said pen means is electrically energized, and said pen means i11- cludes a plurality of energizable pens which are mounted in spaced relationship on an endless band, said bandbeing driven by said means for moving said pen means whereby sairv pens are moved along the second axis with respect to the surface of said recording material.

9. The invention as defined in claim 7 wherein said meaus for detecting different frequency components of the electrical signals includes a heterodyne oscillator having an output signal which is adjustable in frequency according to the movement of said carriage means along the first axis, and a modulator for combining the output signal of said oscillator with the electrical signals from Said microphone means whereby the combined signals can be adapted to energize said pen means.

10. The invention as defined in claim 7 wherein said means `for varying movement speed of said pen means includes filter means for obtaining a predominant sound signal of the periodic sounds, means for applying a power 4signal to said means for driving said pen means along the second axis in response to the predominant sound signal, and means connectably driven with said pen means for stopping said power signal at a predetermined position of said pen means along the second axis with respect to the surface of the recording material whereby the power signal is reduced in average duration when the periodic rate of the predominant sound signal is low and increased in average duration when the periodic rate of the predominant sound signal is low and increased in average duration when the periodic rate of the predominant sound signal is high.

11. The invention as defined in claim 7 including means responsive to a predominant sound signal of said periodic sounds to energize said pen means and produce a rate mark on said recording material for each cycle of the predominant sound signal.

12. A stethoscopic spectrograph, comprising:

recording material having a'surface adapted to be marked;

means for positioning a section of said recording material on a recording platen;

carriage means movable in a lateral direction with respect to the surface `of said recording material; pen means movably mounted to said carriage means and movable in a longitudinal direction with respect to the surface of said recording material, said pen means being energizable to mark the surface of said recording material;

f microphone means adapted to pick up generally periodic sounds and convert the same into electrical signals;

first motor means for moving said vcarriage means laterally with respect to `the surface of said recording material in first and second predetermined directions; means adjustably coupled to said carriage means and responsive to lateral movement thereof in the first predetermined direction, for detecting different frequency components of the electrical signals and energizing said pen means therewith;

second motor means for moving said pen means longitudinally with respect lto the surface of the recording material;

means for reversing movement of said carriage means at first and second predetermined limits of travel thereof; means for de-energizing said second motor means when said first motor means is energized to move said carriae means in the second predetermined direction; an

means for Varying movement speed of said pen means in response to the periodic rate `of a predominant sound of the periodic soun-ds picked up by said microphone means, so that said pen means is moved subystantially equal distances during respective periods of dierent periodic rates -of lthe predominant sound of the periodic sounds whereby recordings of uniform size are produced `over a wide range of different periodic rates of the predominant sound of the periodic sounds.

13. The invention as defined in claim 12 including means for longitudinally moving said recording material to a new section on said platen when said first motor means is energized to drive :said carriage means the vsecond predetermined direction.

14. The invention as defined in claim 12 in which said pen means includes a plurality of electrically energizable A pens which `are mounted in spaced relationship on an endless band, and `said recording material includes paper having a treated surface for producing visible markings thereon when said pens are energized, said band being driven by 'sa-id second motor means whereby said pens are moved longitudinally with respect to the surface of said paper.

15. The invention as defined in claim 12 wherein said means for detecting different frequency components of the electrical signals includes a heterodyne oscillator `having.

an output signal which'is varied in frequency according to lateral movemen-t of said carriage'means, and a modulat-or for combining the output signal of said oscillator with the electrical signals from said microphone means whereby the combined .signals can be adapted to energize said pen means. n

16. The invention as defined in claim 12 wherein said means for varying movement'speed of said pen means includes .filter means for obtaining a predominant sound signal of the periodic sounds, means responsive to the predominant .sound :signal for applying a power signal to said means for moving said pen means longitudinally, and means connectably driven with said pen means for terminating said power signal at a predetermined longitudinal position of said pen means with respect to the surface of the recording material whereby the power signal is reduced in average duration when the periodic rate of the pre-V dominant sound signal :is low and increased in average duration when the periodi-c rate of the predominant sound signal is high. Y

17. The invention as 'defined in claim 1-2 .including means responsive to a predominant sound signal of said Y periodic sounds to energize said pen means and produce rate marks'on said recordinggrnaterial for each cycle of the predominant sound signal. Y

means being energizable to markthe surface of SaidV recording material; Y microphone means adapted to pick up generally periodic isounds'and convert the same into electrical signal; i iirst moto-r means for moving said carriagel means laterally with respect to the surface of said recording E@ material in rst and second predetermined directions between dirst and second predetermined limits of travel;. l Y means adjustablyfcoupled Vto said carriage means and responsive to lateral movement thereof in the'rst predetermineddirection, for detecting ditierent fre- Y quency components of the electrical signals and energizing Said pen means therewith; Isec-ond motor means for moving said pen meansrlongiltudinally with respect to the surface of said recording material; l f an adjustable source of power for energizing said Second motor means to drive said, pen means .at a selected speed corresponding with the periodic rate of a predominant sound of the periodic sounds picked up by said microphone means; and

means for synchronizing,energization of lsaid'second motor means and movement .of said pen means with .a predominant sound signal of theperiorlic sounds whereby said pen'means is moved over the section of said recording material in Synchronism'with appearance of the predominant 'sound signal `of the periodic sounds, Y

19.l The invention as defined in claim .18 including switch means which is actuated when saidrpen means reaches an end of the 'section of said record-ing material to deenergize said second motor means and stop said pen means, said secondrmotor means being energized again on appearance of the predominant 'sound signal of the periodic sounds.

ReferenceSCited by the YExaminer UNITED STATES PATENTS Y' 2,073,457 V3/37 SchWarZchi-ld 179-1 2,689,161 `9/54 Marchand et al. 346-*33 2,770,517 `lll/56 Zabrislcie 346l39 X '2,883,642 4/59 KietZ 346-139 X 2,892,666 `6/59 Parker etal 346-139 X 3,030,946 4/62 Richards 12S-e206 3,048,166 8/62 Rodbard v v 346--33 X 3,052,756 9/62 Seven et al. V a l79-1 LEO SM-ILOW, Primary VExaminer. Y 

1. A STETHOSCOPIC SPECTROGRAPH, COMPRISING: RECORDING MATERIAL HAVING A SURFACE ADAPTED TO BE MARKED; MEANS FOR MOVING SAID RECORDING MATERIAL OVER A RECORDING PLATEN IN A FIRST DIRECTION; PEN MEANS MOVABLE IN A SECOND DIRECTION AT SUBSTANTIALLY RIGHT ANGLES TO FIRST DIRECTION, SAID PEN MEANS BEING ENERGIZABLE TO MARK THE SURFACE OF SAID RECORDING MATERIAL; MICROPHONE MEANS ADAPTED TO PICK UP GENERALLY PERIODIC SOUNDS AND CONVERT THE SAME INTO ELECTRICAL SIGNALS; MEANS FOR MOVING SAID RECORDING MATERIAL AND SAID PEN MEANS AT FIRST AND SECOND SPEEDS, RESPECTIVELY; MEANS COUPLED WITH SAID MOVING MEANS AND ADJUSTABLY VARIED THEREBY FOR DETECTING DIFFERENT FREQUENCY COMPONENTS OF THE ELECTRICAL SIGNALS AND ENERGIZING SAID PENS MEANS THEREWITH; AND MEANS FOR VARYING MOVEMENT SPEED OF SAID PEN MEANS IN RESPONSE TO THE PERIODIC RATE OF A PREDOMINANT SOUND OF THE PERIODIC SOUNDS PICKED UP BY SAID MICROPHONE MEANS, SO THAT SAID PEN MEANS IS MOVED SUBSTANTIALLY EQUAL DISTANCES OVER RESPECTIVE PERIODS OF DIFFERENT PERIODIC RATES OF THE PREDOMINANT SOUND OF THE PERIODIC SOUNDS WHEREBY RECORDINGS OF UNIFORM SIZE ARE PRODUCED OVER A WIDE RANGE OF DIFFERENT PERIODIC RATES OF THE PREDOMINANT SOUND OF THE PERIODIC SOUNDS. 